The JAK2 V617F mutation is found in patients with blood-related diseases such as polycythemia vera, essential thrombocythemia and myelofibrosis. Ruxolitinib is effective as a JAK inhibitor, making it a prognostic factor in determining drug response. Detection of the JAK2 V617F mutation facilitates the classification of patients with MPD (myeloproliferative disease) into three levels of diagnostic certainty (possible, probable and definitive) and to determine which signal transduction therapy is appropriate for each patient. In addition, the WHO (World Health Organization) has recommended JAK2 V617F mutation testing as a clinical trial.